Sometimes a pair lives together with a pair of shrimp which raises
the question how they avoid a collision in the narrow burrow when they
all dart in at the same time at the approach of a predator (Philippines).

This is what happens when a fish doesn't get cleaned in time. The parasite
is now too big to be removed and this Creole Wrasse probably suffers
greatly from it (Caribbean).

Clown fish are clumsy swimmers and brightly colored.
They would be easy prey for predators. So they live in sea anemones
which have tentacles studded with stinging cells that can fire tiny
poisonous harpoons when something touches them. No predator dares to
pluck a clown fish from among these stingers. But why is the clown fish
not stung? Because it absorbs in its skin a chemical from the sea anemone
which the anemone uses to prevent it from stinging itself when the tentacles
touch. This chemical paralyzes the stinging cells so they don't fire
their harpoon (Red Sea).